This invention relates to accessory faucets, or so-called "third faucets", which are usually installed on the sink top to the side of the traditional hot and cold water faucets. The accessory faucet is connected to a source of filtered water usually in the form of the outlet of a reverse osmosis filter.
In such a reverse osmosis filter there is a brine line which is to be connected to waste. Regulations require that there be an air break in the brine waste line. Such an air break, in order not to leak waste onto the kitchen floor in normal operation, is disposed above the sink level. Conveniently it is incorporated in a module in the base of the accessory faucet. This arrangement is disclosed in U.S. Pat. No. 4,635,673 which issued Jan. 13, 1987 to Gerald E. Gerdes, and assigned to our assignee.
The air break module of Gerdes and other air breaks in the art will suitably prevent, on the occasion of a severe drop in building water supply pressure, the siphoning back of material from waste back into the filter chamber through the brine line and thence into the cold water supply system of the building.
However, it does not take care of another recognized serious incident: the occasion of build-up of back pressure created by a blocked-up downstream sewer line. In such an instance a pressure head can be built up in the waste line of the building so that a very positive pressure appears in the brine line outlet, to reverse the flow of liquid in the brine line. In extreme cases this can produce a jet of waste in the module aimed up through the break up into the brine line inlet and thereby cause entry of waste into the upstream side of the filter and again into the cold water system of the building.
In summary, the air break modules in reverse-osmosis filters of the prior art successfully prevented the introduction of waste into the building water supply from upstream siphonage. They have ignored, however, an equally substantive source of contamination: back pressure from downstream blockage.
The invention also involves an improvement in the valve. In the Gerdes patent the in-line valve includes a stem which is two pieces threaded together. In the past, the holding of the lower end of the stem by the frictional engagement of the valve gasket against its seat has occasionally caused an unscrewing of the two parts of the stem as the spout outlet is swiveled in use. This, of course, is undesirable. At the same time, even if the stem has maintained its unity without unscrewing, the frictional drag of the gasket against the seat has made less easy the swiveling adjustment of the faucet outlet.
Finally, the invention includes an improvement in installation. In the Gerdes patent the installation of the valve/module is accomplished by sticking the threaded inlet pipe down through an opening made in the sink top and laboriously from underneath the sink threading upward a nut wide enough to clamp against the underside of the sink about the hole. This has not only been awkward but has been time-consuming.